1. Field of the Invention
This invention relates generally to birdhouses, and more particularly, to a trapdoor with trigger mechanism for selectively trapping undesirable birds in such birdhouses.
2. Description of the Prior Art
Purple martin birds are a highly beneficial species because they are effective destroyers of garden insects and other pests, such as mosquitos. In order to attract such martins to a birdhouse, it is known that the same must be constructed to fairly precise specifications and be kept clean.
Martins will return to nest in the same birdhouse year after year, provided the birdhouse is clean and free of nests, twigs, debris, etc. of other birds upon return of the martins from their annual migration. Undesirable birds, such as sparrows, will occupy martin houses after the martins leave and therefore, it is necessary to regularly clean out the birdhouse to rid the same of the debris placed in the house by the undesirable birds so that the martins will return to nest in the house. Alternatively, traps can be used adjacent to martin houses to attract the undesirable birds and thereby discourage the same from nesting in the martin houses.
It is known to provide bated sparrow traps near the martin birdhouses to help alleviate the problem of sparrows nesting in the martin houses. For example, U.S. Pat. No. 3,778,922 discloses a sparrow trap of the type to be located near a martin birdhouse to capture undesirable sparrows for disposal. There are certain times of the year, however, when a baited trap is not effective since it is not selective in trapping only the undesirable bird species. Therefore, there is a need for a trap to selectively capture sparrows that are nesting or attempting to nest in a specific nesting compartment of a martin house.
It is known to provide a bird trap for use in a compartment of a martin birdhouse in which a trapdoor is substituted for a standard martin house door, except that the entrance hole provided in the door is of a smaller dimension than that which would permit martin birds to enter the compartment. Such prior art traps include a gate member positioned behind the entrance hole and retained in untripped position above the hole by a trigger mechanism which is tripped when a sparrow alights thereon upon entry into the birdhouse.
Problems have been encountered in use of the latter prior art bird traps, illustrated in FIG. 2, because it is difficult to maintain the gate member in untripped position until the bird to be trapped enters the birdhouse compartment. The gate is retained in tripped position by a trip arm engaged against the gate to force it against a compression spring, but the structure is unintentionally released easily by wind movement of the birdhouse or during the process of raising or lowering the same on a mounting post. Furthermore, it is difficult to reset the trigger mechanism of said prior art structure without opening the compartment which is inconvenient.
Traps for capturing animals by using various types of door trapping mechanisms are known in the art. In addition to U.S. Pat. No. 3,778,922 noted above, the following patents are illustrative of such devices:
______________________________________ 1,625,027 2,813,639 2,567,664 3,729,852 2,573,228 ______________________________________
Although these patents describe various traps to capture sparrows and the like to preclude them from nest building activities in birdhouses designed for martins or other selected species, none of these patents is concerned with a trap specifically for use in a martin birdhouse to selectively trap sparrows that are nesting or attempting to nest in the house.
The device of the present invention provides an effective birdhouse trapdoor that can convert a standard birdhouse compartment into a trap for capturing only undesirable birds in that compartment. The invention provides an effective trigger mechanism for releasing the trapdoor which cannot be tripped inadvertently by movement of the house in raising or lowering the same on its mounting pole or by movement in the wind. Furthermore, the invention provides an effective expedient for resetting the trigger mechanism after initial use.